JP2863866B2 - Method for producing unsaturated nitrile-conjugated diene copolymer rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention comprises dispersing a conjugated diene monomer and a nitrile group-containing unsaturated monomer in a suspension in a reaction solution using water as a medium. The present invention relates to a method for producing an unsaturated nitrile-conjugated diene copolymer rubber to be polymerized.

(Prior Art) As a method for industrially producing a rubbery polymer comprising a conjugated diene-based monomer and a nitrile group-containing unsaturated monomer, several methods are conventionally known. For example, there is an emulsion polymerization method in which a conjugated diene-based monomer and a nitrile group-containing unsaturated monomer are emulsified in water with a suitable emulsifier, and a radical polymerization initiator is added thereto to carry out polymerization.
However, the copolymer produced by this method has many residual impurities such as an emulsifier, an inorganic salt, and the like, and has disadvantages such as being corrosive to metals and having poor electrical insulation.

In order to improve such a defect, there is a method of obtaining the copolymer by solution polymerization or bulk polymerization. However, in the case of solution polymerization, a polymer having a high molecular weight cannot be obtained, and a separation step of recovering a solvent from the reaction solution after polymerization is required, which increases equipment costs. In the case of bulk polymerization, since the viscosity of the reaction solution increases with the progress of the reaction, the capacity of the stirrer must be large, and it is often difficult to remove heat, and it is difficult to control the reaction.

Suspension polymerization is known as a polymerization method for remedying these drawbacks. Although there are many examples of resinous polymers, unsaturated nitrile-conjugated diene rubbery polymers are polymerized in a solvent (Japanese Patent Publication No. 50-33519).
The suspension polymerization method using water as a medium has not been attempted so far and has not been practiced industrially because the adhesion and blocking of polymer particles are remarkable.

(Problems to be Solved by the Invention) The present inventors have conducted intensive studies to improve the above points, and as a result, by specifying the stirring conditions during the suspension polymerization reaction,
The conjugated diene-based rubbery polymer formed in the reaction solution is stably dispersed in a suspension state to prevent blockage due to the coalescence of polymer particles, and also to provide an unsaturated nitrile having good coagulation and drying properties. It is intended to provide a method for producing a conjugated diene copolymer rubber.

(Means for Solving the Problems) Thus, according to the present invention, when the unsaturated nitrile-conjugated diene copolymer rubber is obtained by the aqueous suspension polymerization method, the weight ratio of water / monomer in the suspension is determined. 0.1 to 4, and 0.01 to 5 parts by weight of the dispersant with respect to 100 parts by weight of the monomer mixture, and further, such that the tip speed U of the stirring blade defined by the following formula (1) is 1 to 20: And a method for producing an unsaturated nitrile-conjugated diene-based copolymer rubber, characterized in that the polymerization is carried out in the following manner.

U = πDn (1) U; tip speed of stirring blade (m / sec) D; diameter of stirring blade (m) n; rotation speed of stirring blade (1 / sec) (Detailed description of configuration) Water system of the present invention The suspension polymerization method uses water as a medium,
A typical method is to supply a dispersant and a polymerization initiator to a reactor and to carry out polymerization while stirring.

The unsaturated nitrile-conjugated diene copolymer rubber of the present invention includes conjugated dienes such as 1,3-butadiene, isoprene and 1,3 pentadiene; acrylonitrile, and nitrile group-containing unsaturated monomers such as methacrylonitrile; It consists of a monomer and a copolymerizable monomer. Examples of copolymerizable monomers include vinyl aromatics such as styrene, α-methylstyrene and divinylbenzene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid and maleic acid and salts thereof; methyl acrylate, Esters of the carboxylic acids such as ethylhexyl acrylate and methyl methacrylate; alkoxyalkyl esters of the unsaturated carboxylic acids such as methoxyethyl acrylate and methoxyethoxyethyl acrylate; acrylamide, methacrylamide, N-methylol (meth) acrylamide, N Amide monomers such as N, dimethylol (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, cyanomethyl (meth) acrylate,
-Cyanoethyl (meth) acrylate, 2-ethyl-6
-(Meth) such as cyanohexyl (meth) acrylate
Epoxy group-containing monomers such as allyl glycidyl ether, glycidyl acrylate and glycidyl methacrylate.

The composition of each monomer in the polymer is conjugated diene monomer 55 to
90% by weight, nitrile group-containing unsaturated monomer 10-45% by weight,
0 to 20% by weight of a monomer copolymerizable therewith is preferred.
If the content of the nitrile group-containing unsaturated monomer is 10% by weight or less, oil resistance is poor, and if it exceeds 45% by weight, elasticity is poor.

Examples of the dispersant include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose,
Water-soluble cellulose ethers such as hydroxypropylmethylcellulose and carboxymethylcellulose; partially saponified polyvinyl alcohol; water-soluble polymers such as acrylic acid polymers and gelatin; polyethylene glycol fatty acid diesters; starch; tracant gum; gum arabic; Alternatively, they can be used in combination. Although the amount of the dispersant varies depending on the type, the amount of the dispersant is preferably 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the monomer mixture. It is. When the amount is less than 0.01 part by weight, the effect as a dispersant cannot be obtained, and when the amount exceeds 5 parts by weight, the viscosity of the reaction solution increases.

The polymerization initiator is a monofunctional peroxide such as benzoyl peroxide, t-butylperoxypivalate, diisopropylperoxydicarbonate, or acetyl peroxide; 2,5-dimethyl-2,5-di (2-ethylhexa). Noylperoxy) hexane, 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexyne-3,
Bifunctional peroxides such as 1,6-hexanediol-bis-t-butylperoxycarbonate; azo compounds such as 2,2'-azobisisobutyronitrile and the like are used.

The amount of the polymerization initiator to be used is generally 0.01 to 5 parts by weight based on 100 parts by weight of the monomer mixture.

The polymerization temperature varies depending on the type of polymerization initiator or polymerization method, but is usually preferably in the range of 50 to 130 ° C.

In aqueous suspension polymerization of an unsaturated nitrile-conjugated diene copolymer rubber, the tackiness of polymer particles increases as the reaction proceeds. In order to prevent this phenomenon and to stably disperse the polymer, the water / monomer ratio in the suspension is 0.1 to 4, preferably 0.3 to 2.5, and the dispersant is 100 parts by weight of the monomer mixture. On the other hand, it is necessary that the tip speed of the stirring blade defined by the formula (1) is 1 to 20, preferably 2 to 10, more preferably 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight. Keeping the water / monomer ratio and the dispersant amount within the above ranges, respectively,
The suspension is given an appropriate viscosity to increase the dispersion efficiency by stirring. If the water / monomer ratio is less than 0.1, the viscosity of the suspension increases with the progress of the reaction, resulting in blocking of the polymer particles, which is not preferred.

Further, even if the water / monomer ratio and the dispersant amount are maintained in the predetermined ranges, a stable suspension cannot be obtained if the tip speed of the stirring blade is insufficient. The tip speed of the stirring blade must be 1 m / sec or more. If it exceeds 20 m / sec, the power of the stirrer becomes too large, which results in promoting the blocking of the polymer.

In the case of producing an unsaturated nitrile-conjugated diene copolymer rubber according to the present invention, gelation occurs as the reaction proceeds, so that the polymerization conversion rate is desirably 50% or less.

Other conditions of aqueous suspension polymerization, such as water to the polymerization reactor,
The method of charging the monomer, dispersant, polymerization initiator and the like is not particularly limited, and a molecular weight regulator, a chain transfer agent, a pH regulator and the like may be added to the polymerization system as needed.

The molecular weight of the rubbery polymer obtained by the aqueous suspension polymerization of the present invention is not limited, and may be liquid or solid.

(Effects of the Invention) Thus, according to the present invention, it is possible to produce an unsaturated nitrile-conjugated diene-based copolymer rubber by an aqueous suspension polymerization method, which has not been conventionally performed. Compared with the conventional emulsion polymerization method, solution polymerization method and bulk polymerization method, the present invention can easily control the reaction, and can efficiently obtain a high-purity rubbery polymer, which is extremely valuable for industrial use. It is expensive.

(Example) Hereinafter, the present invention will be described more specifically with reference to examples. The parts and percentages in Examples and Comparative Examples are important criteria unless otherwise specified.

Example 1 A cylindrical reactor equipped with a stirrer having a marine stirring blade having an internal volume of 10 was prepared. Two viewing windows were made in the side wall of the reactor so that the inside could be observed. In this reactor, a total of 2160 g of butadiene and 1440 g of acrylonitrile
3600g (100 parts) water 3600g (100 parts) as dispersant
18 g (0.5 parts) of partially saponified polyvinyl alcohol was charged and stirred to prepare an aqueous suspension. Next, 18 g (0.5 parts) of 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane was added as a polymerization initiator, and the reaction temperature was increased.
The reaction was performed at 65 ° C. for 30 hours. Observation from a viewing window revealed that the polymerization was not blocked and maintained a good suspension state. The suspension after the reaction taken out of the reactor was also stable, and the inside of the reactor was clean without adhesion of the polymer.

The removed suspension is dropped into methyl alcohol in which hydroquinone and alkylated phenol are dissolved,
A rubbery polymer was precipitated. The polymerization conversion was calculated from the weight of the polymer obtained by drying under reduced pressure. The Mooney viscosity was measured according to JISK-6300.

3 g of the obtained copolymer rubber was placed in a 150-mesh cylindrical metal mesh, immersed in tetrahydrofuran at room temperature for 48 hours, and the insoluble content (gel content) remaining in the metal mesh was measured. %. Table 1 shows the results.

Examples 2 to 5, Comparative Examples 1 to 4 Using the same apparatus as in Example 1, the total volume of the monomer and water charged into the reactor was adjusted to that of Example 1, and the water / unit Monomer ratio, type of monomer and its ratio,
The stability of the suspension was observed by changing the type and amount of the dispersant, the type and amount of the polymerization initiator, and the tip speed of the stirring blade. Table 1 shows the polymerization conditions and the results.

In addition, the molecular weight of the liquid rubber of Example 3 was measured by high performance liquid chromatography.

As can be seen from Table 1, according to the production method of the present invention,
Since polymer blocking does not occur during the polymerization reaction, the reaction can be easily controlled and a polymer having a low gel content can be obtained.

Claims (1)

(57) [Claims] When an unsaturated nitrile-conjugated diene copolymer rubber is obtained by an aqueous suspension polymerization method, the weight ratio of water / monomer in the suspension is 0.1 to 4 and the dispersant is a monomer. Unsaturated nitrile characterized by being polymerized under the condition of 0.01 to 5 parts by weight with respect to 100 parts by weight of the mixture and further such that the tip speed U of the stirring blade defined by the following formula (1) is 1 to 20: -A method for producing a conjugated diene copolymer rubber. U = πDn (1) U; tip speed of stirring blade (m / sec) D; diameter of stirring blade (m) n; rotation speed of stirring blade (1 / sec)